Finding optimal CCT for smartphone display by K.Choi

Kyungah Choi, a Ph.D. candidate of CED Lab made a presentation entitled, “Optimal color temperature adjustment for mobile devices under varying illuminants” on the IS&T/SPIE Electronic Imaging (EI 2014), CA: Burlingame, USA. This study investigated a proper white reproduction on smartphone display when it was viewed under varying illuminants, particularly when the CCT of the light source varied. Her presentation attracted a lot attention, and was selected one of the best two presentations of the entire session.


With the wide use of mobile devices, display color reproduction has become extremely important. The purpose of this study is to investigate the optimal color temperature for mobile displays under varying illuminants. The effect of color temperature and illuminance of ambient lighting on users’ preference was observed. For visual examination, a total of 19 nuanced whites were examined under 20 illuminants. A total of 19 display stimuli with different color temperatures (2,538 K ~ 19,628 K) were presented on the New iPad. The ambient illuminants ranged between 2,540 K and 19,800 K in color temperature and from 25 lx to 3,078 lx in illuminance. Supporting previous studies on color reproduction, there found to be a positive correlation between color temperature of illuminants and that of optimal whites. However, the relationship was not linear. Based on the 56 subjects’ assessments, a regression equation was derived that predicts the optimal color temperature adjustment under varying illuminants [Display Tcp = 5138.93 log(Illuminant Tcp) – 11956.59, p<.001, R2=0.94]. Moreover, the influence of illuminant was positively correlated with the illuminance level confirming the previous studies. It is expected that the findings of the study could be used as the theoretical basis when designing a color strategy for mobile display devices.